Chill Water Pipe distribution

8/15/2019 Chill Water Pipe distribution

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Improved Chilled Water PipingDistribution Methodology

for Data Centers

Revision 1

by Isabel Rochow

Introduction 2

Characteristics of traditionalhard piping methods

2

Flexible piping methods 6

Comparison between hardpiping and flexible piping

8

Conclusion 13

Resources 14

Click on a section to jump to it

Contents

White Paper 131

Chilled water remains a popular cooling medium;

however leaks in the piping systems are a threat to

system availability. High density computing creates

the need to bring chilled water closer than ever before

to the IT equipment, prompting the need for new high

reliability piping methods. This paper discusses new

piping approaches which can dramatically reduce the

risk of leakage and facilitate high density deployment.

Alternative piping approaches and the advantages over

traditional piping systems are described.

Executive summary>

white papers are now part of the Schneider Electric white paper library

produced by Schneider Electric’sData enter Science enter

[email protected]



Improved Chilled Water Piping Distribution Methodology for Data Centers

Schneider Electric – Data Center Science Center White Paper 131

Rev 1

2

In data centers, the traditional approach to piping distribution has been to use hard copper or

carbon steel piping with welded, brazed or threaded fittings for routing and branching of the

piping to the air conditioners. Since every fitting used in the piping line increases the leak

failure potential in the data center, piping distribution is generally located under the raised

floor where channels or trenches are sometimes built under the pipe to capture water in case

of any leaks or rupture. This approach worked in static data centers, where there was no

need to relocate or add air conditioners.

With the current trend of increased densities in IT equipment and more frequent moves,

additions, and changes, air conditioners must occasionally be added to the traditional lay-out

where the use of hard piping becomes problematic. These additions require new piping to be

installed, increasing deployment time of the equipment and increasing the risk of down time

associated with the installation. The result is that there is a need in the industry for a more

flexible modular system of piping that can better accommodate changing requirements.

A new trend is data centers that do not use a raised floor. These hard-floor installations are

enabled by newer cooling technologies and architectures that do not require a raised floor for

air distribution. For many users this allows additional flexibility of placement of data centersand computer rooms. One result of this trend is that overhead piping has become more

common. Leaks in overhead piping can be even a greater risk to system downtime and

damage than underfloor piping. There is a need in the industry for a more leak-resistant

piping system.

A further trend in data center design is the deployment of cool ing at the IT equipment row

locations (In-row), or even to individual racks, rather than at the room level. This is done to

allow higher density and greater electrical efficiency, and is discusses more completely in

White Paper 130, The Advantages of Row and Rack-Oriented Cooling Architectures for Data

Centers. This type of deployment forces the air conditioning units and the associated piping

closer to the IT equipment. Again this situation requires a more reliable, modular, and

scalable piping system.

The use of seamless flexible piping eliminates the use of intermediate fittings, mitigating the

risk of water leaks, reducing deployment time, and increasing the agility of the system. This

paper explains this new piping technology and its application to next-generation data centers.

The use of hard copper or carbon steel piping is the traditional approach in data centers.

Carbon steel pipe schedule 40 and hard copper pipe type L or M are most commonly used.

Hard piping requires the use of threaded, grooved, welded or brazed fittings at every turn, at

every valve, at every branch to multiple air conditioners and at every 1.8 or 6 meters (6 or 20

feet), depending on the available length of the pipe run. It is common to have multiple fittings

in one pipe run from the chilled water source to the air conditioner.

Failure modes of hard piping

Each threaded or welded fitting presents a leak potential for the chilled water system. One

common reason for leakage is the threading process which removes 50% or more of the pipe

wall beginning on day one and weakens that joint.

Another reason for pipe failure and water leakage is galvanic corrosion, where the carbon

steel pipe directly meets a brass valve, or is transitioned to copper pipe. "Galvanic" corrosion

occurs between any two dissimilar metals in contact with each other and water, and typically

Introduction

The Advantages of Row andRack-Oriented Cooling Architecture s for Data Centers

Related resource

White Paper 130

Characteristicsof traditionalhard piping me-thods

http://www.apc.com/wp?wp=130










Rev 1

3

attacks the steel pipe to a degree somewhat dependent upon existing corrosion conditions. It

is visually recognizable in its latter stages by some degree of deposit buildup where the

dissimilar metals meet at the threads, creating a micro-fine leak. At that point, however, most

of the damage has already occurred and replacement of that pipe is required, otherwise the

leak size would increase as corrosion advances.

Electrically isolating fittings, called dielectrics, are used for connections between dissimilar

metals in most piping systems. Dialectric fittings are specified by most consulting and design

engineers, but it is not uncommon to find installations where they were not installed or they

are installed incorrectly.

In a traditional chilled water installation, it is not uncommon to see a main carbon steel supply

or return pipe that branches to the air conditioners with copper piping, so multiple dielectric

fittings might be used if several computer room air conditioners (CRAC) are in the data

center.

Other less common reasons include the failure of the thread sealant over time, poor machin-

ing of the threads, gasket deterioration in grooved connections and poor quality of the pipe or

fittings, vibration, stress, improper assembly, or excessive operating pressures beyond

design.

In hard piping systems, minerals tend to build up on the interior wall causing scaling and

oxidation of the copper and eventually creating pinholes and leakage in the piping. Mineral

build-up overtime also increases the pressure drop in the water line, especially when it is

deposited in elbows or fittings. To avoid this problem, water has to be treated and main-

tained periodically to ensure proper PH levels. The water is usually treated at the time of

start-up and during regular services. Even though it is rare to see pinholes in a closed loop

chilled water installation, it has been found in installations were poor maintenance was

performed.

Condensation also presents a problem in a chilled water system. Chilled water piping is

usually insulated to prevent condensation in the piping exterior. However, it is not uncommon

to find moisture on the piping fittings where multiple elbows, connections, and fixtures such

as valves, strainers, and gauges make an effective insulation job difficult. Any crack orsealing failure in the insulation presents water potential in the data center and it also be-

comes an entry point for moisture to permeate under the insulation and travel along the pipe

surface for a significant distance.

The presence of condensation at the outer pipe wall in non-conditioned environments also

produces corrosive effects. Exterior corrosion is promoted much more when high humidity

exists in the environment surrounding the pipe. In extreme cases, condensation will build up

to the point where the insulation becomes completely saturated with water. In data centers,

exterior corrosion of the pipe does not usually occur due to the humidity controlled environ-

ment.

To contain any condensation or water in the event of a leak in a data center, some IT

managers and facilities engineers demand additional protection for the IT and electricalequipment. However, this practice is generally not implemented until water becomes a

problem in the data center.

In some instances, the concern about the possible loss of cooling that a single leak would

cause is so great that IT managers opt to install a completely redundant hard piping system

which doubles the total piping installation cost. Alternatively, they opt to install CRACs with a

refrigerant based system as a back-up that also requires additional refrigeration piping.





Rev 1

4

Underfloor hard piping installation

The method for routing chilled water piping depends on the size of the room and the number

of air conditioners. For small rooms, the chilled water piping is usually routed through one

large main supply and return pipe made of carbon steel or copper. For larger rooms, several

large manifolds of carbon steel pipe are used. Each main header or manifold is then

branched with copper piping to each air conditioner. Figure 1 illustrates underfloor hard

piping where multiple fittings are used in the installation.

For this methodology, when the owner is concerned about water under the floor, a trench with

drains is specifically built for the containment of the chilled water piping to separate it from

the electrical wiring. Alternatively, a drain pan can be built underneath each run of piping to

collect any possible leakage or condensation from the system. The depth and width of the

trench is sized depending on the diameter and quantity of the chilled water pipes running in it.

In addition, clearances have to be provided for service of all the different pipes in the trench

in case of a leak. In a medium to large data center it is not uncommon to find deep trenches

up to 1.5 meters (5 feet), to accommodate all the chilled water piping, valves and servicing.

With various distances from the chiller to each air conditioner, start-up of the chilled water

system requires each air conditioner be balanced to provide the correct amount of chilled

water to each of them. The system balancing is accomplished using isolation and balancing

valves which are usually located in the pipe branches under the raised floor; while the

actuated water regulating valves are usually located in the air conditioners. By having

balancing and isolation valves under the floor, balancing the system takes longer since the

balancing valves are not easily accessible.

These systems require one time engineering and they usually remain as static systems due

to the infrastructure needed to route the piping and the difficulty to add an extra pipe line to

the main header once the room is in operation.

If a leak occurs on the main manifold, the mean time to recover (MTTR) increases, since all

CRACs fed from the main branch would loose their chilled water supply. This would cause

the room temperature to rapidly increase, resulting in IT equipment failure or forcing the

equipment to shut down.

Figure 1

Traditional underfloor chilled water piping installation withbranches to different air conditioners using multiple fittings





Rev 1

5

Overhead hard piping installation

This approach also uses a main header or manifold that is branched to each air conditioner

until it arrives to the last system. Isolation valves and balancing valves are usually located in

the pipe branches inside or outside the data center or right above the air conditioners.

Since overhead piping presents the potential of condensation or leakage over the IT equip-

ment, a drain pan is used when the pipe crosses any electrical or IT equipment and in someinstances the operator specifies a drain pan under all the chilled water pipes in the data

center. For these cases, a wide drain pan is provided under the main headers and a smaller

pan is used for branches. This methodology is used due to the potential leak failures and

condensation that the various pipe fittings present and as a precautionary measure, to protect

all the power and IT equipment under the pipe. Figure 2 shows an example of a traditional

installation with overhead piping and drain pans underneath for leakage containment.

With the valves being located above the ceiling or outside the data center, balancing the

cooling system is not easily done. This increases the time required for start-up and balancing

of each unit. In case of leakage in an overhead installation, the repair must be performed

above the equipment installed on the floor, which increases the potential for water on the

floor or worst yet, the equipment.

Double wall piping systems are very seldom used to provide secondary containment. It is

used mostly in cases where local codes require it or when the owner or design engineer

specifies it. The double containment piping system is composed of an outer pipe that

completely encloses an inner carrier pipe in order to contain any leaks that may occur and to

allow detection of such leaks. The procedures and installation requirements for double wall

piping make this methodology extremely expensive, but more effective than using only a

drain pan underneath the piping. Figure 3 shows a side and front cut-away view of a double

wall pipe.

Figure 2

Overhead piping with drain pan above racks

Figure 3

Cut-away view of a double wall pipe





Rev 1

6

Recent advances in piping technology using flexible piping permit chilled water transport into

data centers with greatly improved reliability and dramatically reduced chance of leakage.

This piping is based on a technology that has been used for piping HVAC systems in Europe

for over 30 years. The flexible piping is a multi-layered composite tubing consisting of an

aluminum tubing sandwiched between inner and outer layers of cross-linked polyethylene.

This gives the piping flexibility to be routed through the data center with the rigidity to stay in

place. The cross-linked polyethylene or PEX also offers excellent protection against corro-

sion and the smooth interior walls and chemical properties make it resistant to mineral

buildup with hard or soft water eliminating the risk of pinholes.1

Improved reliability compared with hard piping

The use of flexible piping allows the system to be routed without the use of elbows or any

intermediate joints from the chilled water source to each CRAC. If multiple CRACs are used,

a centralized distribution system allows for multiple connections to a main distribution header

installed in the perimeter or outside the room. The header provides individual isolation,

balancing and branching to each air conditioner in the room, using individual flexible jointless

supply and return pipes. This methodology replaces all the intermediate joints in the data

center with only two joints per supply and return line; one at the distribution header and one

at the CRAC. A traditional hard piping system will have from 10 to 20 joints per supply or

return branch to each air conditioner depending on the pipe run, while a flexible piping

system with only two per line, reduces the leak potential to only 10 or 20% of the hard piping.

By eliminating any intermediate fittings or valves and with a lower thermal conductivity than

copper or steel pipe, flexible PEX piping also significantly reduces the condensation potential

in the data center. This is because condensation usually occurs at pipe fittings, connections

and valves, due to the difficulty to insulate them effectively.

Centralized distribution, when used with flexible piping, greatly reduces the concerns of co-

locating the chilled water piping with IT equipment and of routing overhead piping. Installing

a centralized water distribution system in the perimeter of the room allows all the balancing

and isolation valves to be installed at the same location, thus reducing the time to balance the

complete chilled water system. Dynamic data centers benefit from this approach since

having flexible piping permits the relocation of air conditioners by running the flexible pipe to

the new location. In high density applications the addition of future CRACs can be achieved

by running a line from the main header to the new air conditioners without disturbing the rest

of the chilled water piping.

The actual failure rate improvement over hard piping methods is dramatic. The following is a

quote from one of the leading manufacturers of this tubing system2:

“It has been used in Europe for 30 years, with more than 4 billion feet of installed tubing

performing without a single incidence of product failure. 500 million feet of that is in North America alone. Samples of the tubing have been under high temperature and pressure

continuously since 1973, with no sign of decreased performance. Tests, both by Wirsbo and

independent sources, predict that the Wirsbo PEX tubing should have a system life in excess

of 100 years”

1 Plastics Pipe Institute™ - High Temperature Division, The Facts of Cross-Linked Polyethylene (PEX)Pipe Systems, 12/3/04

2 Shelter Technology, http://www.sheltertech.com/wirsbo_pex_tubing.htm (accessed March 4, 2010).

Flexible pipingmethodology





Rev 1

7

Overhead flexible piping installation

For overhead applications, the flexible piping is routed through the aisles from the distribution

header to the air conditioners and a drip pan is only used when the pipe crosses any

electrical or IT equipment. Accessories are also available on the market that guide several

stacked lines of flexible piping, minimizing the space used overhead for pipe routing. Figure

4 illustrates the use of flexible piping overhead.

Flexible piping dramatically decreases the leak and condensation potential that most owners

have with overhead piping. As data centers opt for overhead wiring and in-row or overhead

cooling, the need for a raised floor and the expense that comes with it are diminished. For

more information on in-row and overhead cooling, see White Paper 132, Comparison of In-

Row vs. Overhead Cooling .

Underfloor flexible piping

The use of flexible piping under the raised floor provides the advantage of having a direct

route from the distribution header to the CRACs. This reduces the pipe distance by having

straight lines to the air conditioners. Flexible piping can be routed under floor heights as

small as 12 inches, and since they usually cross only over power and IT wiring, a drain pan is

not necessary for a straight line to the air conditioners. This reduces the installation cost and

deployment time when compared to traditional underfloor hard pipe systems. Figure 5

illustrates the use of flexible piping underfloor.

Figure 4

Layout drawing of data centerwith flexible piping overhead

Comparison of In-Row vs.Overhead Cooling

Related resourceWhite Paper 132










Rev 1

8

The following sections compare hard and flexible piping against various attributes including

mechanical, physical, agility, availability, total cost of ownership (TCO), and failure modes.

Mechanical and physical attributes of hard piping and flexible piping

Table 1 provides a list of the main mechanical and physical attributes of the flexible piping

and hard piping used for chilled water systems.

Figure 5

Underfloor flexible pipinginstallation with branches todifferent air conditioners

Comparisonbetween hardpiping andflexible piping





Rev 1

9

Physicalattributes

Carbon steelschedule 40

Hard copperpiping type “L”

Flexible pipingPEX

Pipe weight in kg per linearmeter (2.54 cm nominalsize pipe without water)

2.49 0.975 0.324

Pipe weight in pounds perlinear foot (1” nominal sizepipe without water)

1.67 0.655 0.218

Temperature rating Up to 399°C (750°F) Up to 204°C (400°F) Up to 93°C (200°F)

Rated internal workingpressure in megapascal

19.7 MPa @ 38°C19.7 MPa @ 93°C

3.41 MPa @ 38°C2.79 MPa @ 93°C

1.38 MPa @ 23°C0.689 MPa @ 93°C

Rated internal workingpressure in psi

2857 psi @ 100°F2857 psi @ 200°F

494 psi @ 100°F404 psi @ 200°F

200 psi @ 73°F100 psi @ 200°F

Type of fittingsWelded, brazed, grooved

or threaded fittings

Soldered, brazed,grooved or threaded

fittings

Multipress threaded orcompression fittings

Size range3.2 to 660 mm

(1/8” to 26”)6.4 to 305 mm

(¼” to 12”)

12.7 to 5.08 mm (½ ” to 2”)in North America

12.7 to 609 mm (½ ” to 24”)in Europe

3

Termination connectionWelded, brazed or

threaded

Soldered, brazed or

threaded

Multipress threaded or

compression

Corrosion resistance

Limited, depends on therelative humidity of theenvironment and PH of

water

Very good Excellent

Thermal conductivity High High Medium to Low

Agility and availability of hard piping and flexible piping

New technologies such as blade servers are resulting in IT loads that are greatly exceeding

the rated cooling system capacity, resulting in the need for additional cooling in the data

center.

Hard piping does not provide flexibility for future expansions. In order to keep the existing air

conditioners operational, a new pipe line is usually branched from the chiller to the additional

units. The installation cost and deployment time are high due to the difficulty to route piping

in a building that has an existing chilled water system and the difficulty to braze or thread new

3 Shelter Technology, PEX piping for Plumbing” presented at 40

th ASPE convention, Oct 2004,

http://www.plasticpipe.org/media/PEX_ASPE_2004.pdf#search='wirsbo%20pex%20pipe%20sizes (accessed March 4, 2010).

Table 1

Physical attributes of hard and flexible piping





Rev 1

10

joints in an existing data center. Even if the air conditioners will only be relocated, a new

hard pipe line must be routed from the branching header to the new location, which again

involves multiple brazed or threaded joints.

Flexible piping provides the agility and availability for the addition or relocation of equipment.

A flexible pipe is installed without the need for fittings or brazed joints from the distribution

header to the CRAC location. Since the balancing and isolation valves are installed in the

header and the main piping from the chiller to the header is already installed, there is no

downtime for the existing chilled water system and deployment time is reduced due to the

simplicity of the pipe installation.

A failure or leak on the hard pipe main supply or return from the chi ller to the data center

would require the shutdown of all the air conditioners in order to repair the failure which can

take from several hours to days. This would have the same effect if a distribution header is

used, since hard piping is also used from the chiller to the header. If a failure were to occur

on that pipe, all the CRAC piping from the header would also require shutdown until the

failure is repaired. If a leak or failure occurs in a hard piping system on one of the sub-

branches from the main pipe, just the air conditioners branched from that pipe loose chilled

water when the line is isolated for repair. Repairing a hard piping system requires the

isolation and interruption of cooling at all the CRACs tied to that pipe and usually the leaking

component is replaced or the fitting is brazed again at the point of leakage.

With flexible piping, if a leak occurs from the distribution header to the air conditioner, only

one air conditioner would require shutdown for repair, without interrupting cooling in any of

the other air conditioners. If a leak occurs at the distribution header fitting or at the CRAC

fitting, the fitting is replaced. However, if a leak occurs in the flexible pipe line itself, a repair

would mean that the entire flexible pipe must be replaced. The new pipe would be replaced

by isolating the line at the centralized distribution system and at the air conditioner, interrupt-

ing cooling at that single CRAC without interrupting cooling in any of the other air condition-

ers.

Total cost of ownership of hard piping and flexible piping

The total cost of ownership is reduced with the use of flexible piping and a centralized

distribution header compared to a brazed pipe system. A 200 kW data center with a new

cooling system installation would obtain an increased speed of deployment of at least 40%

and an installation cost reduction of approximately 20% if it is performed with flexible piping

and a centralized distribution header. This reduction in installation cost is a result of not

having additional labor for brazing intermediate fittings and installing intermediate valves, as

well as a reduction in time to balance the chilled water system.

In an existing data center, the installation of one additional air conditioner from the distribu-

tion header using flexible piping reduces the installation cost by at least 50% and the

deployment time by 60% compared to a traditional brazed piping system.

Maintenance of a chilled water system using flexible piping is easier and faster to performsince the inspection of all the valves is done in a centralized location, while in an underfloor

installation, these valves are located at different areas of the data center.

In data centers where the raised floor is used only for the routing of chilled water pipes, the

elimination of the raised floor further reduces the capital expense of the installation if an

overhead piping system is used. Table 2 compares hard and flexible piping as they relate to

the benefits that data center users have identified as the most important for a chilled water

piping system.





Rev 1

11

Hard piping Flexible piping

Agility

Slow speed of deployment due to multiple brazed jointsrequired.

Balancing of system is not easily accessible either under theraised floor or above the ceiling t iles.

Non-scalable expansions or relocations require one timeengineering and downtime for other units.

Increased speed of deployment by 40%.

Balancing of the water system is located in a centralizedaccessible location.

Scalable, allows for moves, adds, changes, and futureexpansions without disturbing other units.

Availability Leak potentials at every fitting and joint decreasing reliability.Increased reliability by eliminating intermediate joints drasticallyreducing leak potential.

MTTR

If leakage occurs on the main, repair may take from hours todays depending on the leak.

If leakage occurs on a distribution branch in the data center,repair may take several hours, causing shutdown for severalunits.

If leakage occurs from the chiller to the centralized distributionheader, repair may take from hours to days depending on theleak.

If leakage occurs on a flexible branch in the data center, newflexible piping can be routed and repair may take up severalhours causing shutdown on one unit only.

Installation

Higher installation costs. System balancing requires more timeadding cost to start-up.

Brazed, threaded, or mechanical joints and fittings are used,and intermediate isolation and balancing valves are required.

Lower installation cost. System start-up and balancing is lesscomplex with the centralized distribution system.

No brazed joints, intermediate fittings, or valves are required.

Turning radius Allows a shorter turning radius using elbow fittings.Minimum bending radius is 5 to 7 times the outside diameter ofthe tube.

Maintainability

Visual checks for leaks at each joint and valve, visual check forcondensation at fittings and valves and visual check at

corrosion points. Water and glycol concentration measured andvalidated.

Less time spent in visual checking for leaks and condensationformation on valves at the centralized distribution header (all

valves are in one location). Water and glycol concentrationmeasured and validated, routine maintenance

Pressure dropThe use of elbows for turns and mineral buildup causesadditional pressure drop

Smooth interior and larger radius turns without fittings reduce thepressure drop for typical piping runs

White space Piping is run underfloor or overhead, no white space isoccupied by the piping system

White space is required for the centralized distribution header inthe room.

Distances Long pipe distances can be performed with hard pipe sinceseveral pieces of pipe are joined through fittings.

Maximum distance recommended is 46 meters (150 ft) from thedistribution header to the air conditioners due to the complexitythat longer distances would create for the installer.

Upfront cost(installation

and material)

Hard pipe cost is lower but the overall installation cost is higherdue to the increased labor required for brazing and threads and

system balancing requires more time adding cost to start-up.

PEX piping has a higher cost, however the overall installationmay be lower due to the elimination of brazing or threaded fittingsand the system start-up and balancing is less complex with thecentralized distribution system.

Pipe location Can be installed outdoors or exposed to sunlight.PEX must not be stored or installed in areas where it is exposedto sunlight, either direct or indirect.

Table 2

Comparison of hard and flexible piping

Note: shading indicates best performance for the characteristics





Rev 1

12

Failure mode comparison for hard piping and flexible piping

A chilled water system may encounter different failure modes depending on the location of

the piping, the type of installation, and the piping methodology used. Table 3 summarizes

the possible failure modes for each type of piping and the best performance is highlighted.

Hard piping Flexible piping

Punctures Less susceptible to leakage due to puncture by a sharp object. More susceptible to leakage due to puncture by a sharp object.

Single pointfailures

Failure in a branching pipe causes loss of cooling in all CRACsconnected to the branch.

Failure in a line causes loss of cooling in only one CRAC.

Joint leaks

Multiple joints and fittings in the pipe increase leak potential dueto possible galvanic corrosion, failure of thread sealant over

time, poor machining of the threads, gasket deterioration ingrooved connections or poor quality of the threaded fittings.

Reduced amount of joints - two per line per CRAC. Multipressthreaded fittings crimp the PEX-AL-PEX tube making a stronger

connection than a threaded or gasketed fitting.

Earthquake /vibration

Vibration or earthquake movement can cause leakage at jointsand fittings.

Less susceptible to break or leak in vibration or earthquakeconditions.

Stepping onMay damage brazed or threaded fittings which can produce aleak.

Less susceptible to damage due to the flexibility of the pipe.

Insulationdripping fromcondensation inthe data center.

More potential for condensation due to difficulty to insulatemultiple valves, strainers, and fittings. Small cracks or spacesleft without insulation may cause condensation.

Less potential for condensation due to the elimination ofintermediate valves or fitting between the distribution system andthe CRACs.

Abrasions / cuts Resistant to exterior abrasions or cuts Less resistant to exterior abrasions. Cut can damage the PEXpiping exterior.

Pinholes andmineral buildup

Susceptible to pinholes and leakage due to mineral buildup ifwater is not treated periodically.

Very resistant to mineral buildup due to smooth interior walls andchemical properties.

Table 3

Failure mode comparison of hard and flexible piping

Note: shading indicates best performance for the characteristics





Rev 1

13

Even though hard piping for chilled water systems has been used as the traditional solution,

using a centralized distribution header with individual flexible lines to each air conditioner

significantly improves the reliability of the system since the leak potential is drastically

reduced. Also, a failure in a flexible pipe system will only require isolation on one CRAC

which allows the rest of the units to continue cooling the load, while a failure in a hard piping

system may require isolation of several CRACs if the failure is in one of the branching pipes,

jeopardizing the availability of the data center without enough cool ing to support the load.

The concern of water in the data center is also reduced with a flexible piping system for three

reasons:

1. The overall piping system failure rate is greatly decreased due to the dramatic reduc-

tion in joints

2. The fundamental reliability of the base piping itself is higher

3. The potential for condensation is reduced by not having intermediate fittings or valves

to insulate, which are the main points of condensation formation in a chilled water sys-

tem.

Flexible piping is an enabling technology for hard floor data center installations and for row-

oriented and rack-oriented high density cooling systems. The trends toward higher density

and hard floor installations will naturally result in a rapid increase in the use of flexible piping

for next-generation data centers.

Conclusion

Special thanks to Isabel Rochow for authoring the original content of this white paper.

Acknowledgements




The Advantages of Row and Rack-OrientedCooling Architectures for Data Centers

White Paper 130

Comparison of In-Row vs. Overhead Cooling

White Paper 132

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